Blade type cartridge fuse



Dec- 16, 1958 G. A. BARRETT ETAL BLADE TYPE CARTRIGE FUSE Filed April 2.1958 Fig/J Gefld A Baffett tevsorw Attorneg.

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United States BLADE TYPE CARTRIDGE FUSE Application April 2, 1958,Serial No. 725,927

Claims priority, application Canada July 23, 1957 7 Claims. (Cl.200-132) This invention relates to a cartridge fuse and moreparticularly to a contact structure therefor.

Circuit interrupting fuses of the general class to which this inventionrelates employ a tubular cartridge enclosing a fusible element connectedto a blade type contact projecting from, and supported by, each end ofthe cartridge. It is well known to employ a solid strip of electricallyconductive material, such as copper, for the contact. When the fuse isin an electrical circuit each of its contacts is received between a pairof fingers of a clip, the fingers being spring biased toward each other.Since these fuses are generally required to carry relatively highcurrents, considerable heat may be generated at the areas of engagementbetween the fuse contacts and the fingers of the clips. After anextended period of heating the engaging surfaces will oxidize, followedby an increase in resistance, and nally an increase in heating at thesurfaces. Repeated heating and cooling will eventually relax the springtension in the fingers of the clip thus further increasing theresistance ybetween the fuse Contact and the lingers.

Hitherto, it has been general practice to design blade type fusecontacts large in mass in order to obtain satisfactory heat dissipatingcharacteristics, and this mass was usually considerably greater thanthat necessary to carry the current flowing through the fusible element.As metals of good electrical and thermal conductivity, such as copper,are relatively expensive, massive fuse contacts add appreciably to thecost of a fuse. Accordingly, therefore, it is an object of thisinvention to provide a blade type Contact structure for a cartridge fusein which the quantity of metal used is reduced to the minimum requiredfor mechanical strength and electrical conductivity.

lt is another object of this invention to provide a ventilated bladetype contact structure within which ambient air may freely circulate todissipate heat from the Contact.

A further object of this invention is to provide a blade type contactwhich will yield on -being inserted between a pair of contact receivingfingers.

A still further object of this invention is to provide a novel means forsecuring a blade type contact to the cartridge of a fuse.

Brieiiy, this invention consists of a hollow blade type contact securedat one end thereof to the midpoint of a pin, the longitudinal axes ofthe Contact and the pin being perpendicular or somewhere nearperpendicular` The ends of said pin rest in a pair of diametricallydisposed apertures in the wall of a fuse cartridge adjacent an endthereof so as to be more or less iiush with the outer peripheral surfaceof the cartridge. A ferrule adapted to close the end of the cartridgehas a flange overlying the end of the cartridge and the ends of the pin,the iiange being indented in a manner to cooperate with the pin tomaintain the pin and ferrule assembled to the cartridge. An aperture inthe ferrule permits the contact to project through the ferrule from theend of arent O reice the cartridge. Both ends of the fuse cartridge areprovided with one of the aforementioned contact structures and they arejoined by a fusible element. l

The invention will be fully understood and its objects and advantagesbetter appreciated by referring to the following detailed descriptiontaken in conjunction with the accompanying drawings, in which Fig. l isa view of a cartridge fuse with one end of the cartridge and one contactstructure in section;

Fig. 2 is a view in perspective of a hollow Contact of tubular form;

Fig. 3 is a view in perspective of a hollow contact of corrugated form;and

Fig. 4 is a View in perspective of one end of a cartridge fuse with aportion of the cartridge and ferrule broken away to show the contactsupport means, and also a contact receiving clip.

Figure l illustrates a cartridge fuse having a tubular cartridge 1enclosing a fusible element 2 connected between a pair of blade typecontacts 3 and 4 projecting from the ends of the cartridge. Blade 3 issupported on a tubular pin 5 whose end 6 rests in an aperture S in thewall of cartridge 1 and whose end 7 rests in an aperture 9 in the wallof the cartridge, aperture 9 being disposed diametrically oppositeaperture 8. Pin 5 is of such a length that its ends 6 and 7 aresubstantially flush with the outer peripheral surface of cartridge 1.Blade 4l is supported in a similar manner on a tubular pin 10 whose endsrest in a pair of diametrically disposed apertures in the wall ofcartridge 1.

A ferrule 11, with an aperture 12 through which the contact 3 passes,closes off the open end 13 of cartridge 1. The ferrule has an integralannular flange 14 which overlies end 13 of the cartridge and also ends 6and 7 of pin 5. Indentations 15 and 16 in flange 14 are deformed intothe ends 6 and 7 respectively of tubular pin 5. It is thus apparent thatpin 5 supports blade 3 and the pin in turn is supported in apertures 8and 9 in the wall of the cartridge, the whole Vbeing maintained inassembled relationship -by means of ferrule 11. I Blade 4 and pin 10 arealso maintained assembled to cartridge 1 in a similar manner by means ofa ferrule 17.

Blades 3 and 4 are identical. Blade 3 is illustrated in perspective inFigure 2 as comprising a contact formed from a length of electricallyconductive tubing :flattened along its length to provide a pair ofparallel side walls 18 and 19 joined by curved edge walls 2t) and 21.One end of the flattened tube is pinched off at 22 to provide a fiatportion 23 where the inner surfaces of side walls 18 and 19 touch. Flatportion 23 is apertured at 24 to permit the securing of contact 3 to pin5 in a manner to be described later. By referring to Fig. 1 it will beseen that the end of contact 3 which projects from the end of cartridge1 is hollow from the left hand tip thereof to region 22 where thepinch-off begins, flat portion 23 closing otf the right hand end of thecontact. This hollow is designated by the numeral 25 in Figures l and 2.

`In place of the contact blade structure 3 shown in Figure 2 a contact3a, such as that shown in Figure 3, may be used. The contact 3aillustrated in Figure 3 may be formed from a rectangular sheet ofelectrically conductive material by corrugating the sheet along itslength from end 26 to region 27 adjacent the other end of the sheet.Crests 28 of the corrugations on one side of the Contact 3a lie in aplane 30 while crests 29 on the other side of the contact lie in a plane31 parallel to plane 30. One edge of the corrugated sheet may be turnedin as shown at 32 to lie in plane 30 while the opposite edge may beturned in as shown at 33 to lie in plane 31. Although, in Figure 3,crests 28 and 29 of contact 3a are shown parallel to the long axis ofthe Contact, or parallel to the longitudinal axis of cartridge 1, it isto be understood that the directio-n which the corrugations run inrelation to the contact is unimportant so long as .their crests lie inplanes and 31. IIt is not necessary that the corrugations be parallel toone another. The liat end portion 23a of the sheet between region 27 andend 34, which has not been corrugated, is apertured at 24a to permit thesecuring of contact 3a to pin 5 in a manner to be described later.

The pin 5 is cut to a length about equal to the outer diameter of thecartridge from tubing having an outer diameter slightly less than thediameter of aperture 24 or 24a. To assemble contact 3 to the cartridge,aperture 24 in the contact is aligned with apertures S and 9 in thecartridge, and pin 5 is then inserted into these aligned apertures suchthat its ends 6 and 7 are substantially 'Hush with the outer peripheralsurface of the cartridge. Thereafter while holding contact 3 centrallypositioned on pin 5, both ends of the pin are diametrically expandeddown to the flat portion 23 on the contact. Expansion of tube 5 may -beeffected by well known means as by forcing an oversized mandrel intoeach end of the tube to form shoulders and 36 on pin 5 between which thellat portion 23 of contact 3 is wedged thereby rigidly securing the pinto the contact. Assembly of contact 3a to pin 5 and to the cartridge maybe carried out in a similar manner.

Fusible element 2 may be soldered to the contacts to provide a lowresistance current path. When contacts such as 3 and 4 are used the endsof the element 2 may be sandwiched between the walls of the contactadjacent the aperture 24 as illustrated at 37 in Figure l. The latterconnection may be a pressure contact where the expanding of pin 5provides the pressure through shoulders 35 and 36. For ease of assemblyelement 2 will usually be secured to the contacts before the contactsare secured to pins 5 and 10.

Figure 4 illustrates one type of spring clip 40 having a base 41apertured at 42 so that it maybe bolted to a support (not shown). Cliphas a pair of parallel contact receiving fingers 43 and 44 integrallyunited with base 41 through curved nger offsets 45 and 46 respectively.`Clip 4t) is formed from an electrically conductive resilient materialin such a manner that base 41 cooperates with olfsets and 46 to biaslingers 43 and 44 toward each other. As edge 21 of contact 3 is insertedinto clip 40, lingers 43 and 44 yield and thereby permit the outersurfaces of side walls 18 and 19 of the contact 3 to wipe along theinner surfaces of fingers 44 and 43 respectively thus providing a goodelectrical junction between the contact and the clip.

Since the contact 3 is made of a relatively thin walled material whichmay exhibit some resilience, and since the portion of contact 3 receivedwithin the fingers of clip 40 is hollow, the contact 3 will also yieldon being inserted into the clip. In view of the fact that the contact,as well as the clip, is resilient it may be possible, under certaincircumstances, to eliminate the back-up springs wihch are often providedto cooperate with the lingers of the clip to maintain adequate pressurebetween the contact and the clip.

The construction of contact 3a is also such that its corrugations willyield or flex on applying pressure to the sides of the contactperpendicular to planes 30 and 31, .as by means of lingers 43 and 44 ofclip 40. It is to be noted that crests 28 and 29 of the corrugationsmake line contact with the inner surfaces of fingers 43 and 44respectively.

Since cartridge fuses of the type to which this invention relatesusually carry relatively high currents, considerable heat may begenerated between the fuse contacts and the contact receiving clips,particularly when the spring tension exerted by the lingers of a clipagainst a fuse contact relaxes due to age or repeated heating andcooling at the points of electrical contact. A fuse contact of the typeshown in Figures l and 2 has a relativelyr thin side wall of good heatconductivity whose inner surface of hollow 25 is exposed to thesurrounding atmosphere. Air is therefore permitted to enter the open endof the hollow and circulate through it thus removing at least a portionof the heat generated in the contact.

As has been pointed out contact structure 3a (Figure 3). makes linecontact with fingers 43 and 44 at points 28 and 29 respectively. Thecorrugations or furrows in contact 3a combine with the inner surfaces oflingers 43 and 44 to define a plurality of ducts along the length of thecontact which are open to the surrounding atmosphere at tip 26 thereof.In place of the one hollow 25 in contact 3 contact 3a has a pluralityyof open ended hollows through which air may circulate to remove heatfrom the contact.

lt is to be understood that the term hollow as applied to the Contactstructures of this invention includes the type of hollows provided bycontact 3a when in place between the fingers of a contact receiving clipas well as the hollow 25 in contact 3. Ambient air may also becirculated through tubular pin 5 by perforating the bottom ofindentations 15 and 16 as shown at 38 and 39 respectively in Figure l.Since contact 3 or 3a is firmly secured to pin 5 some of the heatgenerated in the contact will be conducted to the pin and dissipatedtherefrom to the air circulating through the pin. Although circulationof air is permitted through pin S and in the hollow of contact 3 or 3athe pin, the ferrule and contact close off the end of cartridge 1against any appreciable escape of arc gases generated within the fuse,the aperture 12 being just large enough to permit the contact to passfreely through it.

While preferred embodiments of the invention have been shown anddescribed by way of illustration, many modifications will occur to thoseskilled in the art. Therefore it is contemplated that the claimsconcluding this specication shall cover all such modications as fallwithin the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. -A cartridge fuse construction having a cartridge which includes ateach end thereof a pair of oppositely disposed apertures in its wall; apin disposed in said apertures; a ferrule closing `off the end of saidcartridge, said ferrule having a flange overlying the end of saidcartridge and the ends of said pin and an indentation in said flangecooperating with an end of said pin to maintain said cartridge, pin andferrule in assembled relationship; yieldable hollow blade type conta-ctmeans secured at one end thereof to said pin and projecting through theferrule from the end of said cartridge; and a fusible link inside saidcartridge connected between said contact means at one end of thecartridge and contact means at the other end of the cartridge.

2. A cartridge fuse construction having a tubular cartridge whichincludes at each end thereof a pair of diametrically disposed aperturesin the tube wall, a tubular pin disposed in said apertures with the endsof the pin substantially flush with the outer surface of the cartridge,a ferrule closing olf the end of said cartridge, an annular flange onsaid ferrule overlying the end of said cartridge and the ends of saidpin, indentations in said flange deformed into the hollow ends of saidtubular pin to maintain said cartridge, pin and ferrule in assembledrelationship, a yieldable hollow blade type contact secured at one endthereof to said pin and projecting 4through an aperture in the ferrulefrom the end of said cartridge, and a fusible link inside said cartridgeconnected between said contact at one end of the cartridge and a contactat the other end of the cartridge.

3. A cartridge fuse construction having a tubular cartridge whichincludes at each end thereof lirst and second diametrically disposedapertures `in the tube wall, a tubular pin disposed in said first andsecond apertures with the ends of the pin flush -with the outerperipheral surface of the cartridge, a ferrule closing or the end ofsaid cartridge, an annular flange on said ferrule overlying the end ofsaid -cartridge and the ends of said pin, indentations in said angedeformed into the hollow ends of said pin to maintain said cartridge,pin and ferrule in assembled relationship, a generally tubular contacthaving a pair of parallel side walls, the side walls at one end of saidcontact being flattened together to form a at portion but the other endof said contact being open, a third aperture in said at portion, saidpin being disposed in said third aperture, outwardly expanded shoulderson said pin between which said flat portion is wedged to thereby supportthe contact on the pin, an aperture in said ferrule through which saidcontact projects from the end of the cartridge, and a fusible linkinside said cartridge connected Ibetween said contact at yone end of thecartridge and a 'contact at the other end of the cartridge.

4. yA cartridge fuse construction having a tubular cartridge whichincludes at each end thereof first and second diametrically disposedapertures in the wall of said cartridge, a tubular pin disposed in saidrst and second apertures with the ends of the pin flush with the outerperipheral surface of the cartridge, a ferrule closing off the end ofsaid cartridge, an annular ange on said I'ferrule overlying the end ofsaid cartridge and the ends of said pin, indentations in said angedeformed into the hollow ends of said pin to maintain said cartridge,pin and ferrule in assembled relationship, a corrugated contact havingthe crests of the corrugations on one side thereof in a iirst plane andthe crests on the other side of the contact in a second plane parallelto the rst plane, a flat end on said corrugated contact, a thirdaperture in said ilat end, said pin being disposed in said thirdIaperture, outwardly expanded shoulders on said pin between which saidflat end is wedged to thereby support the contact on the pin, anaperture in said ferrule through which said contact projects from theend of the cartridge, and a fusible link inside said cartridge connectedbetween said contact at one end of the cartridge and a contact at theother end of the cartridge.

5. A cartridge fuse construction having a tubular cartridge -whichincludes at each end thereof a pair of diametrically disposed aperturesin the tube wall, a tubular pin disposed in said apertures with the endsof the pin substantially ilush with the outer surface of the cartridge,a ferrule closing off the end of said cartridge, an annular flange onsaid ferrule overlying the end of said cartridge and the ends of saidpin, indentations in said flange deformed into th-e hollow ends of saidtubular pin to maintain said cartridge, pin and fcrrule in assembledrelationship, the bottoms of said indentations being apertured toprovide an open passage through the flanges of the ferrule into saidtubular pin, a yieldable hollow blade type contact secured at one endthereof to said pin and 5 projecting through an aperture in the ferrulefrom the end of said cartridge, and a fusible link inside said cartridgeconnected bet-Ween said Contact at one end of the cartridge and acontact at the other end of the cartridge.

6. A cartridge fuse construction having a tubular cartridge whichincludes at each end thereof first and second diametrically disposedapertures in the tube wall, a tubular pin disposed in said first andsecond apertures with the ends of the pin ush with the outer peripheralsurface of the cartridge, a ferrule closing ot the end of saidcartridge, an annular ange on said ferrule overlying the end of saidcartridge and the ends of said pin, indenta tions in said flangedeformed into the hollow ends of said pin to maintain said cartridge,pin and ferrule in as sembled relationship, a generally tubular contacthaving a pair of relatively thin side walls disposed in spaced-apartparallel planes and yieldable in a direction generally perpendicular tosaid planes, the side walls at one end of said contact being flattenedtogether to form a at portion but the other end of said contact beingopen, a third aperture in said flat portion, said pin being disposed insaid third aperture and being diametrically expanded along its lengthfrom each side of said at portion thereby rigidly to secure the Contactto the pin, an aperture in said ferrule through which said Contactprojects from the end of the cartridge, and a fusible link inside saidcartridge connected between said contact at one end of the cartridge anda contact at the other end of the cartridge.

7. A cartridge fuse construction having a tubular cartridge whichincludes at each end thereof rst and second diametrically disposedapertures in the wall of said cartridge, a tubular pin disposed in saidrst and second apertures with the ends of the pin flush with the outerperipheral surface of the cartridge, a ferrule closing off the end ofsaid cartridge, an annular flange on said ferrule overlying the end ofsaid cartridge and the ends of said pin, indentations in said flangedeformed into the hollow ends of said pin to maintain said cartridge,pin and ferrule in assembled relationship, an elongated corrugatedcontact having the crests of the corrugations on one side thereof in arst plane and the crests on the other side of the contact in a secondplane parallel to the rst plane, the corrugations being arranged so thattheir crests um parallel to the longitudinal axis of the contact, a flatend on said corrugated contact, a third aperture in said flat end, saidpin being disposed in said third aperture, outwardly expanded shoulderson said pin between which said ilat end is wedged to thereby support thecontact on the pin, an aperture in said ferrule through which saidContact projects from the end of the cartridge, and a fusible linkinside said cartridge connected between said Contact at one end of thecartridge and a Contact at the other end of the cartridge.

References Cited in the file of this .patent UNITED STATES PATENTS1,107,861 Stout Aug. 18, 1914 1,237,211 Leveen Aug. 14, 1917 2,255,926Muller-I-Iillebrand et al. Sept. 16, 1941

